
Serial Communications Interface (SCI)
Technical Data
MC68HC08AZ32A — Rev 1.0
204
Serial Communications Interface (SCI)
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MOTOROLA
For an 8-bit character, data sampling of the stop bit takes the receiver
9 bit times
×
16 RT cycles + 10 RT cycles = 154 RT cycles.
With the misaligned character shown in
Figure 15-9
, the receiver
counts 154 RT cycles at the point when the count of the transmitting
device is 9 bit times
×
16 RT cycles + 3 RT cycles = 147 RT cycles.
The maximum percent difference between the receiver count and the
transmitter count of a slow 8-bit character with no errors is
For a 9-bit character, data sampling of the stop bit takes the receiver
10 bit times
×
16 RT cycles + 10 RT cycles = 170 RT cycles.
With the misaligned character shown in
Figure 15-9
, the receiver
counts 170 RT cycles at the point when the count of the transmitting
device is 10 bit times
×
16 RT cycles + 3 RT cycles = 163 RT cycles.
The maximum percent difference between the receiver count and the
transmitter count of a slow 9-bit character with no errors is
170
163
–
170
Fast Data Tolerance
Figure 15-10
shows how much a fast received character can be
misaligned without causing a noise error or a framing error. The fast
stop bit ends at RT10 instead of RT16 but is still there for the stop bit
data samples at RT8, RT9, and RT10.
Figure 15-10. Fast Data
154
-------------------------
147
–
154
100
×
4.54%
=
-------------------------
100
×
4.12%
=
IDLE OR NEXT CHARACTER
STOP
R
R
R
R
R
R
R
R
R
R
R
R
R
R
R
R
DATA
SAMPLES
RECEIVER
RT CLOCK
F
Freescale Semiconductor, Inc.
n
.